Radar sensors in a frequency band from approximately 76 GHz to approximately 77 GHz are being used to an increasing extent in systems for detection of surroundings, in particular in motor vehicles which have modern driver assistance systems. Conventional sensor generations are used for the long-distance range (detection range up to approximately 250 m) including strongly focusing systems, the detected objects being detected only in a narrow angle range, for example, less than approximately ±30° with respect to the vehicle axis.
A plurality of novel functions, which are to be covered by future systems, require radar sensors having large aperture angles and thus a wide field of view. The aforementioned functions may include, for example, detection of crossing pedestrians/cyclists, intersection assistants, monitoring of a rearward area of the vehicle, monitoring of dead angles, etc.
Radar sensors are therefore installed at various locations in the vehicle, for example, in all four corners of the vehicle, in addition to the front sensors, which are already present. These sensors should implement different directions of emission in deviation from the sensor axis to achieve the greatest possible range and precision laterally in an angle range of approximately ±60°, for example. With today's sensor generations, the antennas are mostly situated in a planar arrangement on a circuit board. Such an arrangement is readily suitable for focusing the transmission/receiving power at a right angle to the circuit board.
Conventional automotive radar sensors have two transmitting antennas and four receiving antennas. More than one transmitting antenna must be used to implement different fields of view. With so-called corner sensors, which are installed in the two front corners of the vehicle, two identical weakly bundling antennas are used for a wide angular field of view in one detection direction. In contrast thereto, conventional so-called rear sensors, which are installed in the two rear corners of a vehicle, have two strongly bundling antennas, which implement a narrow field of view. It is a disadvantage that two different types of sensors, each having specific directional characteristics, are required for covering all four corners of the vehicle.